Category Archives: reading research

“Watch & Learn!” – Systematic Reviews of Non-experimental Studies

Today’s top tip: Want to find the strongest research evidence for your project?   Go to & add the strongest type of research designs as one of your search terms. For example, add the terms meta-analysis or systematic review to your other search terms. **********************************************

Now to the new!  What is a systematic review of descriptive studies? [Note: For information on stronger levels of research “I like my coffee (and my evidence) strong!)]Cat Fishbowl2

First, remember that in a descriptive study, the researcher merely watches or listens to see what is happening. Descriptive studies do not test interventions.

Second, a systematic review (not to be too silly) is a review that is done systematically in order to include all literature on a particular topic . The authors will tell us where they searched for studies, what search terms they used, and what years they searched. That way we can feel sure that all relevant articles are included.

Therefore, in a systematic review of descriptive studies the authors

  • Collect non-experimental studies related to the problem they are trying to solve,
  • Critically review them, &
  • Write up that analysis for you and me.

You won’t see a lot of numbers or statistics in these reviews of non-experimental studies.

Systematic review of descriptive studies are weaker than other levels of evidence in part because they are critical reviews of non-experimental studies in which the researchers only observed subjects. Those non-experimental studies that they are reviewing may be quantitative with results reported in numbers or qualitative with results reported in words.

Here’s an example with results reported in words (qualitative): Yin, Tse, & Wong (2015) systematically reviewed studies for what factors affect RNs giving PRN opioids in the postop period.   They searched publications 2000-2012 and ended up with 39 relevant studies. Within those 39 articles were descriptive studies that identified 4 basic influences on opioid PRN administration by RNs to postop patients: “(i) nurses’ knowledge and attitudes about pain management; (ii) the situation of nurses’ work practices in administrating range orders for opioid analgesics; (iii) factors that influenced nurses’ work practices; and (iv) perceived barriers to effective pain management from the nurse’s perspective.” [note: In this study a few of the 39 studies were experimental in which something was done to subjects and then outcomes measured, and Yin et al., commented separately on what those showed.]

Critical thinking: What are key differences between a meta-analysis of randomized controlled trials and a systematic review of QUESTIONdescriptive studies?

Reference found with search terms: review of descriptive studies nursing pain – Yin, H.H.,Tse, M.M., & Wong, F.K. (2015). Systematic review of the predisposing, enabling, and reinforcing factors which influence nursing administration of opioids in the postoperative period. Japan Journal of Nursing Science, doi: 10.1111/jjns.12075.



Cohort & Case-controlled studies: Going forward & backward

Got a clinical problem?  You probably want to solve it with evidence—STRONG evidence.   Click on this link to see one well-accepted hierarchy from strongest #1 to weakest #7 (Melnyk & Fineout-Overholt, 2005).   Today let’s look at the 4th strongest level of evidence = Case controlled or cohort studies

First a quick review

Click here for a quick review of the strongest 2 levels of evidence (#1 Systematic reviews, Meta-analyses, or Evidence-based clinical practice guidelines based on systematic review of RCTs. #2 Randomized controlled trials)

Click here for a review of the 3rd strongest type of evidence (#3Controlled trials without randomization)

Now on to the new “stuff”  strong

All 3 of the top, strongest levels of evidence are experimental studies (or include available experimental studies). That means the researcher actually does something or gives a treatment to some of the subjects and then records the outcomes. 

The weaker 4 levels of evidence are non-experimental designs. This means that the researcher merely observes & does Not do anything to subjects. So how does that work?!

First, a cohort study (non-experimental). A cohort study starts with a group of people who have something in common and then the researcher observes only & keeps collecting data from them over a long time into the future. Data collection into the future is called a prospective study. An example is the Nurses’ Health Study, in which over 20,000 nurses were identified and followed-up annually with tests and surveys for over 25 years (this study is still ongoing). These studies provide very valuable information, but are obviously very expensive and time-consuming.”(OMERAD EBM course, 2008)

Now a case-controlled study (non-experimental).  In a case controlled study the researcher observes only & collects data over time into the past (not the future). Data collection into the past is called a imagesCAH6C8NTretrospective study. Again, from the OMERAD EBM (2008) site this example: “Patients with a disease are identified who have suffered a bad outcome such as death or recurrence, and compared with patients who have the disease but haven’t suffered the bad outcome. For example, a researcher might  identify a group of breast cancer patients who have died…, and compare them with a similar group of patients with breast cancer who are still living.”

Critical thinking: Which of these would be better for casQUESTIONe-controlled study and which for cohort study.

  1. You are a runner in the Los Angeles marathon and you are interested in how that race can improve cardiovascular health among those who finish. Question: Cohort or Case controlled?
  2. Some finishers of the LA marathon die of heart attacks 20 years later; many survive another 40 years.   Question: Cohort or Case controlled?

For more info see:


You Got A Problem With That? Try PICO*


  • The Purpose of evidence-based practice (EBP) =  BEST PATIENT CARE, &
  • The Definition of EBP = Best evidence + Clinical judgment + Patient/Family preferences & values

THEN…How do I get started with EBP to improve patient care?

One of the 1st steps is to identify clearly the clinical issue that needs solving.   One way to do that is by using PICO.*

WHAT IS PICO?   PICO is an acronym to help you clarify the clinical problem & to help you prepare to search the literature for evidence

  • P = Patient population or problem
  • I = Intervention or treatment that you want to try out & is based in best evidence
  • C = Comparison intervention or treatment (This might be some standardized care on your unit; or un-standardized care given by individual nurses based on their individual expertise)
  • O = Outcome you want to achieve.

EXAMPLE:  Let’s say you work with post-op patients and want to speed up patients’ return of normal GI function.  Right now on your unit, patients are NPO post-op progressing to ice chips and so on as their bowel sounds start returning.  But you have 2 concerns: a) some patients’ GI function seems quite slow to return; & b) quicker return to a nutritious diet may speed healing.  You read an article that gum chewing can reduce the time of postoperative ileus.  With that information, here is how your PICO problem would look:

  • P = Postoperative patients with ileus
  • I = Gum chewing postop
  • C = NPO with gradual diet progression when bowel sounds start returning
  • O = Reduce time of postop ileus with sooner return to nutritious eating

CRITICAL THINKING: Now you try it.  What is problem for patients (or nurses) on your unit? Try writing it out in a sentence or two and then put it into PICO format.  You are now on your way with beginning an EBP project that will promote the very BEST PATIENT CARE.

Want to read more on PICO?  Try out

*Note: Some use PICOT that includes “T”.  The “T” stands for the time it will take to show an outcome.  Because the timing does not seem to me relevant to all questions I typically omit it, but you may find it helpful.  If so, use it!


What’s an RCT anyway?

  • Question: What is a randomized controlled trial (RCT)? And why should I care?
  • Answer: An RCT is one of the strongest types of studies in showing that a drug or a treatment actually improves a symptom or disease. If I have strep throat, I want to know what antibiotic works best in killing the bacteria, & RCTs are one of the best ways to find that answer.

In the simplest kind of RCT, subjects are randomly assigned to 2 groups.  One group gets the treatment in which we are interested, & it is called the experimental group.   The other group gets either no treatment or standard treatment, & it is called the control group.  

Here’s an example from a study to determine whether chewing gum prevents postoperative ileus after laparotomy for benign gynecologic surgery:  A total of 109 patients were randomly assigned to receive chewing gum (n=51) or routine postoperative care (n=58).  Fewer participants assigned to receive chewing gum … experienced postoperative nausea (16 [31.4%] versus 29 [50.0%]; P=0.049) and postoperative ileus (0 vs. 5 [8.6%]; P=0.032).* There were no differences in the need for postoperative antiemetics, episodes of postoperative vomiting, readmissions, repeat surgeries, time to first hunger, time to toleration of clear liquids, time to regular diet, time to first flatus, or time to discharge. Conclusion?  Postop gum chewing is safe & lowers the incidence of nausea and ileus! (Jernigan, Chen, & Sewell, 2014. Retrieve from PubMed abstract)

Do you see the elements of an RCT in above?

Let’s break it down.

  • Randomized means that 109 subjects were randomly divided into 2 or more groups. In above case, 51 subjects ended up in a gum chewing group & 58 were assigned to a routine care, no gum group.  Randomization increases the chance that the groups will be similar in characteristics such as age, gender, etc.   This allows us to assume that different outcomes between groups are caused by gum-chewing, not by differences in group characteristics.
  • Controlled means that 1 of the groups is used as a control group. It is a comparison group, like the no-gum , standard care group above
  • Trial means that it was a study. The researchers were testing (trying) an intervention and measuring the outcomes to see if it worked.  In this case the intervention was gum chewing and the measure outcomes were nausea and ileus.

Why should you care about RCTs?  Because RCTs are strong evidence that an intervention works (or doesn’t) for your patients

Critical Thinking Exercise:   Go to   In the blank box at the very top enter a few key words about the problem in which you are interested + RCT.  For example:  music pain + RCT.   Then read 1 or more of the abstracts looking for random assignment (randomized), control group, and whether it was a study (trial).   You’re on your way!    -Dr.H

*Note: You may remember from other blogs that p<.05 means the difference between groups is probably cause by the intervention—in this case gum chewing.

“Which Came 1st–The chicken or the egg?” (or, Why Correlation is Not Causation)

Correlation is not causation. RNs who want to use research in practice must take this seriously.

What does it mean?   Answer: Just because two things happen together, we cannot say that one causes the other.

Consider the example of drinking coffee and staying awake. The more coffee you drink, the more hours you will stay awake.   But isn’t it also true that the more hours you try to stay awake, the more coffee you will likely drink?

Thus, in a study about coffee drinking and sleep, you may read that coffee and hours of being awake are correlated. In other words, they occur together. When one goes up, the other goes up.   What is not clear is whether the coffee is causing the person to be awake longer, OR whether being awake longer is causing the effect of more coffee consumption.   The unsolved mystery is: “Which is the cause and which is the effect?”[1]

Likewise consider the consistent relationship between chickens and eggs. Every egg was produced by a hen. Every one. In statistical terms this means that on a scale of 0 to 1 (with 0 being no relationship whatsoever and 1 being a relationship that occurs 100% of the time) eggs and chickens have a perfect 100% relationship of 1. (A statistician would write this as r=1.0).   What is unclear is whether (when the world was young), the chicken appeared first and caused the first egg, or the egg came first and caused the first chicken. Again the unsolved mystery is: “Which is a cause and which is the effect?”

Okay, so let’s do some critical thinking about actual research.  You read these results:

“More calls for assistance related to less fall-related patient harm. Surprisingly, longer response time to call lights also related to fewer total falls and less fall-related patient harm. Generally speaking, more call light use related to longer response times.”[2]

When you read this article, what should you be assuming about the researchers’ findings in terms of relationships instead of cause-and-effect? (Hint: Think about chickens & eggs, or coffee & insomnia.)

[1] Bonus info: We call causes “independent variables” and we call effects, “dependent variables”

[2] Tzeng, H.M,. & Yin, C.Y. (2009). Relationship between call light use and response time and inpatient falls in acute care settings. Journal of Clinical Nursing, 18(23), 3333-3341. doi: 10.1111/j.1365-2702.2009.02916.x. Epub 2009 Sep 4.